In the same saucepan over medium heat, add butter.
After butter has melted, add flour and cook about 1-2 minutes to make a roux.
Slowly add chicken broth and whisk to combine.
Add lemon juice, salt, pepper, thyme, rosemary, marjoram, parsley, sage, poultry seasoning and half-and-half and whisk again.
Allow sauce to heat until thickened, whisking frequently.
Once the sauce has thickened, check for seasoning.
Add additional salt and pepper or other seasonings, if desired.
Pour sauce over top of chicken and mushroom mixture in baking dish.
Cover with foil.
Bake about 45-60 minutes at 350°, until chicken is cooked through.
Garnish with fresh parsley or thyme, if desired.
Serve over cooked rice, mashed potatoes or noodles.